Fertility treatment such as in-vitro fertilisation (IVF) does not increase a woman's risk of cancer despite the hormones used, researchers have found.
Some previous studies had suggested that fertility drugs might be linked with breast, uterine and ovarian cancers.
However, a large study from the University of Lund in Sweden found far fewer women developed one ore more cancers following IVF compared to those who had not had such treatment.
In research reported in 'Human Reproduction,' scientists analysed data from 24,000 women who gave birth after IVF between 1982 and 2006.
They compared rates of cancer in these women to 1.4 million women in the general Swedish population who also gave birth over that period.
Fewer than two per cent of women in the IVF group developed one or more cancers during an average follow-up period of 8 years, compared to close to five per cent of the other group.
After accounting for maternal age, the number of previous pregnancies and smoking status, the overall risk of cancer was about 25 per cent lower for women who had IVF.
'A couple who needs IVF does not have to be afraid that the hormone treatment used - at least those used in Sweden - will carry a risk for the woman to develop cancer,' study leader Dr Bengt Kallen said.
While the risk of ovarian cancer was more than twice as high in the women who had IVF as those who didn't, Dr Kallen suggested that this may be due to abnormalities in ovarian function that could both increase the risk for cancer and the risk for infertility, thus the need for IVF.
'The risk for two common cancers, breast and cervical, was significantly lower than expected,' he said.
He added that this might be due to women who get IVF being healthier than average or, more likely, that IVF-treated women may undergo more cervical and mammography exams.